1. Field of the Invention
The present invention generally relates to a device that decides the status of use of a seat, such as whether a person is seated on the seat or baggage is put on it, and more particularly relates to a device that controls the operation of a passive safety device such as an air bag device and a seat belt device according to the status of use of the seat, especially in cars.
2. Description of the Related Art
Passive safety devices are practically used to prevent passengers from colliding with the internal structure of their vehicles and to protect them when a vehicular accident occurs. Specifically, a passive safety device contains an air bag device and a seat belt device. The air bag device inflates an air bag between a passenger and the structure inside a vehicle if the vehicle is involved in a collision. This air bag functions as a cushion, catches the passenger, and prevents the passenger from colliding with the structure. The seat belt device secures the passenger to the seat and prevents the passenger from colliding with the structure. In particular, in recent years, seat belt devices with pretensioners have also been in practical use. These type of seatbelts secure passengers to seats more firmly by pulling in a predetermined length of a seat belt when vehicles collide. In addition, vehicles equipped with these passive safety devices on the front passenger seat as well as the driver""s seat are in practical use.
The conventional passive safety device operates when vehicles collide even if a passenger is not seated on a seat, especially the front passenger seat. This operation is meaningless because the following problems arise. During repair, the dashboard (instrument panel) which stores the air bag, as well as the operated device, must be replaced, and so the repair cost is increased.
In Japanese Patent Laid-open Publication No. Hei 6-206514, there is disclosed a device that measures a distance from the predetermined position of a car body, for example, from the ceiling unit over the head of a passenger toward the seat and detects the presence of the passenger based on this distance.
In the device described in the publication, even when an attempt is made to detect the presence of a passenger based on the distance from the ceiling unit to the passenger, if baggage is put on the front passenger seat this might incorrectly be detected as the passenger seat. Besides, whether a child seat is installed forward or backward and whether or not a child is seated on the child seat cannot be sufficiently decided merely by measuring distance.
The present invention was made to solve the above mentioned issues. It is an object of the present invention to provide a status-of-use decision device for a seat that decides the status of use of the seat, and a passive safety device for the front passenger that appropriately operates based on the decision of this decision device.
In order solve the above issues, one status-of-use decision device for a seat related to the present invention has a distance measurement device that measures the distance from an upper predetermined point to predetermined multiple points on the seat and around the seat and obtains distance information, and a photographing device that photographs a range including at least a part of the seat and obtains picture information. It also has means for educing contours from the picture information and means for deciding the status of use of the seat based on the distance information and the shapes of the contours. According to the shapes of the educed contours, it can be used to decide to a certain extent whether the contours are those of the seat, those of an object put on the seat, or those of a passenger seated on the seat. Besides, because two-dimensional objects such as patterns of the seat and shades projected on the seat can be eliminated, the accuracy of decision is improved.
The status-of-use decision device for a seat can also have a seat movement sensor that detects movement by adjustment of the seat and a device that corrects the distance information based on the movement of the seat. It is known that seats equipped in vehicles can be moved forward and backward and up and down and that the angle of recline of the seats can be changed, and the obtained distance information differs depending on these movements. By providing the seat with a movement sensor and distance information correction device, the movements can be changed, thereby improving the accuracy of decision.
The status-of-use decision device for a seat can also have a device that calculates a fatigue change of the shape of the seat and allows the distance correction device to correct the distance information based on the movement of the seat and the change in shape of the seat. Accordingly, a fatigue change of the seat shape can also be suppressed, thereby improving the accuracy of decision.
Another status-of-use decision device for a seat related to the present invention has a device that photographs a range including at least a part of the seat and obtains picture information, means that detects the edge of the relevant picture based on the picture information, and means that decides the status of use of the seat based on the shape of the said edge. Herein, an edge is the portion where the difference of the picture information such as the light and shade of adjacent picture elements is particularly large, and this edge tends to collectively appear in the vicinity of the edge of an object. The seat and the shape of the object put on the seat can be accurately decided based on the shape of this edge.
The status-of-use deciding means that makes a decision based on the shape of the edge can decide that there is no person seated on a seat when the shape of the edge that appears in the vicinity of the edge on the seat side of the seat is detected.
The status-of-use deciding means that makes a decision based on the shape of the edge can decide that there is a person seated on a seat when the shape of the edge that appears in the vicinity of the contours of the legs of the person seated on the seat is detected. In particular, the accuracy of decision can be improved by making a decision based on the shape of the edge related to the seat side of the seat and that related to the legs of the person seated on the seat.
The status-of-use deciding means that makes a decision based on the shape of the edge contains an inclination calculation means that calculates the inclination of the edge and a frequency calculation means that calculates the frequency of occurrence for each inclination of the edge, and can determine the frequency of occurrence of the edge based on the shape of the edge.
The frequency calculation means can be made to divide the range of the photographed picture lengthwise and breadthwise by a predetermined number, and calculate the frequency of occurrence of the vertical edge for each column of the individual divided picture and that of the horizontal edge for each row.
Another status-of-use decision device for a seat related to the present invention has a photographing device that photographs the range including at least a part of the seat and obtains picture information, a memory that stores at least one typical picture for each status of use of the seat within the photographing range, and means that compares the picture information and the typical picture and decides the status of use of the seat. Each picture information actually obtained and the typical picture are compared, and the status of use to which more similar typical pictures belong is decided as the status of use of the current seat.
The status-of-use decision device has means that detects the edge of the relevant picture based on the picture information and generates an edge picture, and makes a decision through a comparison with the typical picture to decide the status of use of a seat by comparing the edge picture. The edge picture represents the difference of the picture information such as the brightness with adjacent picture elements in brightness. For example, the portion where the difference in the brightness of adjacent picture elements is large, that is, the portion where the edge is steep, is displayed in white, and the portion where the difference is small is displayed in black. In this case, for a stored typical picture, an edge picture can previously be stored or a normal picture can be stored and the edge picture can also be generated each time.
The status-of-use decision device can also be made to have a seat movement sensor that detects movement caused by adjustment of the seat and means that decides the typical picture to be compared based on the movement of the seat. Because the position of the seat in the photographed picture varies when the seat moves, the typical picture to be compared also needs to be changed accordingly. The configuration of the present invention can solve this problem.
Another status-of-use decision device of a seat related to the present invention can have a device that photographs a range including at lease a part of the seat and obtains the picture information, a memory that stores the picture information, and means that decides the status of use of the seat by comparing the picture information stored in the memory before a predetermined time and the picture in formation photographed at the current time. By comparing the previous picture information and the current picture information, the presence of movement can be detected and thus the presence of a passenger can be decided.
The status-of-use decision device that makes a decision based on the change of picture information has a movement area specifying unit that specifies the area with a large picture change by comparing the picture stored before the said predetermined time and the picture photographed at the current time, and can decide the status of use of the seat based on the position of the specified area.
Another status-of-use decision device of a seat related to the present invention has a temperature distribution photographing device that photographs a range including at least a part of the seat in the infrared region and obtains the temperature distribution and means that decides the status of use of the seat based on the temperature distribution. If there is a person seated on the seat, because the body surface of the person seated on the seat reaches the approximate temperature of the body, this can be detected.
The passive safety system that is another mode related to the present invention has at least one of the status-of-use decision devices of seats described above. Under the predetermined conditions, the passive safety device has a passive safety device that protects passengers from collision with the structure inside vehicles and a control unit that controls the operation of the passive safety device according to the status of use of the seat. If the passive safety device is provided with multiple status-of-use decision devices, it is desirable that predetermined weighting be applied to the decision results of each decision device and the status of use be comprehensively decided.